從文件中讀取下一行

Question

所以程序應該從文件中讀取，文件中有4-5行信息。我可以讀入程序的第一行，並通過各種算法進行處理，但我不確定如何將下一行循環並處理，並一次又一次地處理，直到文件結束。非常感謝您的閱讀和所有的輸入是讚賞。這是整個程序，從文件底部讀入文本。

#include <iostream> 
#include <fstream> 
#include <string> 
using namespace std; 

int main() 
{ 
    ifstream inputFile; 
    ofstream invoicefile; 
    string name, author, isbn, customerid, filename, fictionoutput, genreoutput; 
    char booktype, genre; 
    bool fictionvalue; 
    double initial_total, tax_price, subtotal, totalprice, price; 
    int fee, quantity; 
    const double tax(0.07); 

    cout << "Enter name of file.\n"; 
    cin >> filename; 
    cout << "Opening file \n"; 
    inputFile.open(filename); 

    if (inputFile.is_open()) { 
     inputFile >> customerid >> name >> author >> isbn >> price >> quantity >> booktype >> genre; 

     //QUANTITY FEE CODING BLOCK 
     if (quantity > 50) { 
      fee = 50; 
     } 
     else if (quantity >= 15 && quantity <= 19) { 
      fee = 40; 
     } 
     else if (quantity >= 10 && quantity <= 14) { 
      fee = 30; 
     } 
     else if (quantity >= 5 && quantity <= 10) { 
      fee = 20; 
     } 
     else if (quantity < 5) { 
      fee = 10; 
     } 

     //BOOKTYPE CODING BLOCK (FICTION or NON-F) 
     if (booktype == 'F') { 
      fictionvalue = true; 
     } 
     else if (booktype == 'N') { 
      fictionvalue = false; 
     } 
     else { 
      cout << "INVALID"; 
     } 
     //BOOKTYPE INTO STRING OUTPUT 
     if (fictionvalue = true) { 
      fictionoutput = "Fiction"; 
     } 
     else if (fictionvalue = false) { 
      fictionoutput = "Non-Fiction"; 
     } 

     //GENRE TYPE INTO STRING OUTPUT 
     if (genre == 'R') { 
      genreoutput = "Romance"; 
     } 
     else if (genre == 'D') { 
      genreoutput = "Drama"; 
     } 
     else if (genre = 'M') { 
      genreoutput = 'M'; 
     } 
     else { 
      cout << "Invalid entry\n"; 
     } 

     //NO FEE EXCEPTION 
     if (booktype == 'N' && genre == 'R') { 
      fee = 0; 
     } 


     //CALCULATION OF PRICE + TAX CODING BLOCK 
     initial_total = (price*quantity); 
     tax_price = (initial_total * tax); 
     subtotal = (initial_total + tax_price); 
     totalprice = (subtotal + fee); 



     //OUTPUT TO FILE/CONSOLE CODING BLOCK 
     cout << "-----------------------------------------" << endl; 
     cout << "Order Invoice" << endl; 
     cout << "Customer ID: " << customerid << endl; 
     cout << name << " " << author << " " << fictionoutput << " " << genreoutput << " " << quantity << "@" << price << "Subtotal: " << endl; //add subtotal price 
     //cout << "Total book sales: " << 
     cout << "Tax: " << tax_price << endl; 
     cout << "Subtotal: " << subtotal << endl; 
     cout << "Fee: " << fee << endl; 
     cout << "Total Price: " << totalprice << endl; 

     cout << "-----------------------------------------" << endl; 
     system("pause"); 
    } 

} 

文字示例

1234 Dog_Strategy Henry_Moreno 3-598-21500-2 12.99 5 N M 
6789 Companion_Kicked_Me_Out Lorraine_Johnson 3-598-21599-1 24.99 3 F R 
3444 Mime_On_My Journey Kristy_Wahl 3-699-21500-8 6.75 10 N D 
4455 Damaged_By_The_Joke Henry_Christopher 3-598-21500-2 12.99 4 N R 

Answer 1

也許嘗試使用這樣一個循環：

// Create an empty string 
std::string line; 

// Start a loop that will get a line from the file and input it in our string 
// this loop will keep going until the getline fails, i.e. end of file. 
while (std::getline(fileName, line)) 
{ 
CODE 
} 

Answer 2

，你可以把一個while循環將運行，直到程序看到文件

結束

while(!EOF) 
{your code here} 

永遠不要忘記關閉您打開的文件